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This study presents a numerical investigation of the reflectivity of a Single Anti-Reflective Layer (SARL) and a stack of antireflective layers made of porous silicon. The stack consists of a certain number of periods, and each period contains two layers with different porosity. The simulations were conducted using the well-known Stratified Medium Theory (SMT) framework and the effect of porosity was studied. The optimal value was determined at 60% for the SARL and 65/55% for the stack of 12 periods and 6 layers. The angle of incidence was found to have more influence on the stack reflection than on the SARL reflection. The results of this investigation show that porous silicon can be used as an effective anti-reflective coating for silicon solar cells.

This paper presents ab initio calculations within the Density Functional Theory (DFT) for the structural and optoelectronic properties of the alkali metal hydrides LiH and NaH in rocksalt structure (B1). This study used the Generalized Gradient Approximation (GGA) of Wu-Cohen to consider the electronic exchange and correlation interactions. In addition, the Tran-Blaha modified Becke-Johnson exchange potential was used with the GGA approach (GGA-TBmBJ) to calculate the band structure with high accuracy. The structural properties, namely the lattice parameter, the bulk modulus, and the pressure derivative of the bulk modulus were determined and found to be generally in good agreement with other research findings. Furthermore, the energy band gaps, the Density Of States (DOS), the static and high-frequency dielectric constant, along the refractive index were addressed and analyzed. These results could be useful for hydrogen storage purposes.

A computational study based on the density functional theory calculations is carried out for the band structure and optical spectra of bulk, tri-layer, bi-layer and monolayer CdS system in the hexagonal-wurtzite structure. The aim of this contribution is to see how the electronic and optical properties of CdS change when moving from the bulk form to the monolayer one through tri-layer and bi-layer Cds systems. Our results show that the monolayer form still has a direct (Г-Г) band gap, but with an increased magnitude with respect to that of bulk CdS. The optical properties of the tri-layer, bi-layer and monolayer form are found to be different from those of the bulk form. An anisotropic character has been shown by the optical spectra for light polarized parallel and perpendicular to the x axis of the crystal. Our findings indicate that novel electronic and optical properties may be obtained when passing from bulk to tri-layer, bi-layer and monolayer CdS system.

Cette note de lecture porte sur La spiritualité, un facteur de performance du leadership de l’enseignante-chercheure Faviola Tapoyo. Il s’agit de la publication de sa thèse en sciences humaines et sociales. Ce travail de recherche qui se déploie entre la France (Montpellier) et le Gabon (Libreville) présente la particularité de réfléchir l’investissement spirituel du dirigeant dans son leadership, la place et le rôle de la spiritualité dans la conduite des organisations et la recherche de la performance. This review covers the book La spiritualité, un facteur de performance du leadership by the research teacher Faviola Tapoyo. This book is her the thesis on social and human sciences. Her research, between France (Montpellier) and Gabon (Libreville) has the particularity to question the spiritual investment of managers in their leadership, and the place and role of spirituality in the management of organizations and in the search for performance.

Here, we report the synthesis and study of new orange-red (OR) colour-emitting phosphors Na2 ZnP2 O7 :xTb3+ (x = 1, 1.25, 1.5, and 1.75 mol%) using a conventional solid-state reaction. The sample crystallographic structures and their room temperature photoluminescence properties were measured using X-ray powder diffraction, excitation and emission spectra, as well as emission decay curves. X-ray diffraction analysis showed an isostructural tetragonal structure for all the doped materials with no impurities. Several colour emissions corresponding to 5 D4 →7 F6 (blue), 5 D4 →7 F5 (green), 5 D4 →7 F4 (orange) and 5 D4 →7 F3,2,0 (red) intraconfigurational transitions were observed and investigated. These colours were dominated by the OR colours. 5 D4 energy level lifetime was independent of Tb3+ concentration. Various radiative and luminescence parameters, such as experimental branching ratio, radiative decay rate, and luminescence quantum efficiencies, were calculated and discussed. Chromaticity diagram calculations illustrated an orange emission for all the studied materials.